Bathing compositions which foam upon exposure to warm water have found wide consumer acceptance due to the enhanced cleaning power of the foam produced and the cosmetic aspects such as appearance, fragrance and emollience which can be imparted by the ingredients commonly incorporated therein. Liquid bathing compositions, or "bath oils," are available as aqueous solutions or dispersions of mineral oil, wheat germ oil, thickeners, fragrance and the like, which are formulated to incorporate an effective amount of one or more foam-producing surfactants.
Although such liquid compositions can function effectively to foam bath water, their general availability in bulk (bottled) form poses a number of problems. In the first place, the appropriate amount must be pre-measured and poured into the bath water stream, a step which often results in waste or spillage. In the second place, bottled bath oils are bulky and inconvenient to transport. Although the large excesses of water employed to formulate the compositions promote their dispersion in the bath water, the water also increases the shipping weight and storage space required for liquid bath oil compositions.
Soft gelatin encapsulation of a liquid foaming bath oil composition could remedy these deficiencies, providing easily-transportable "unit doses" of the composition in concentrated form. Soft, elastic (SEG) gelatin capsules are stable for long periods under ambient conditions while rupturing readily when exposed to warm water. However, soft gelatin, i.e. of type A or B, is chemically destabilized by alkaline salts, leading to the leaking or bleeding of the capsule contents at elevated pH. This property has heretofore prevented the soft gelatin encapsulation of bath oil compositions such as those which include commonly-used foaming surfactants such as the fatty acid (diethanol)amides. These surfactants exhibit pH's of greater than about 8.0-8.5 as measured in aqueous solution.
Therefore a need exists for a concentrated, high-foaming bath composition which is suitable for, and compatible with, a soft gelatin shell.